This invention relates generally to apparatus for use in the manufacture of solar cell arrays for converting solar radiation to electrical energy. More particularly, this invention relates to an automated, multistation machine for precision placement and attachment of electrically conductive interconnectors onto individual solar cells at a relatively high production rate.
Solar cells are relatively well known for use in converting incident solar radiation into electrical energy. A typical solar cell comprises a relatively thin sheet of doped silicon semiconductor material supported upon a thin metallic backing, with a thin and narrow conductive contact strip extending along the top surface of the semiconductor sheet at one marginal edge thereof. The substantial majority of the top surface of the semiconductor sheet is thereby exposed to incident solar radiation and constitutes an active or light-sensitive surface which responds to the incident radiation to produce a relatively small electrical current and voltage. A large number of these individual solar cells are commonly mounted side by side onto a generally planar substrate of extended surface area and are appropriately connected electrically in series and in parallel to form a solar cell array having selected electrical power generating characteristics. Solar cell arrays of this general type have constituted an important source of electrical power in a wide variety of environments, including, for example, the provision of electrical power in long term satellites.
Individual solar cells within a solar cell array have thus required an electrically conductive component, commonly referred to as an interconnector, for electrically coupling the solar cell with adjacent solar cells in the array. Such interconnectors commonly comprise a relatively thin and lightweight metallic ribbon chosen for thermal compatibility and high quality connection as by soldering with the metallic backing and/or the conductive contact strip on a solar cell, thereby minimizing risk of solar cell breakage during use which would result in an electrical open circuit within the solar cell array. Moreover, several interconnectors are frequently used with each solar cell to provide multiple or redundant electrical connections which further decrease and substantially eliminate risk of electrical open circuits. Such redundant connections within a solar cell array are particularly desirable in an outer space environment, since access to the array for repair purposes is impractical or impossible.
In the manufacture of solar cells for use in a solar cell array, a plurality of interconnectors is commonly attached by soldering or welding onto the conductive contact strips of individual solar cells as an intermediate steps in the manufacturing process. Such interconnector installation requires relatively high precision to insure correct interconnector placement and attachment onto a solar cell within relatively close tolerance limits. Moreover, such installation must be performed without damaging the solar cell which is typically extremely fragile, with solar cells of the type used in outer space environments having extremely thin thicknesses on the order of 200 microns. In the past, however, interconnector placement and attachment has required a significant degree of manual labor including manual handling of both the solar cell and the interconnectors. Such manual procedures have proven undesirably tedious and time consuming resulting in relatively slow production rates and correspondingly undesirable high costs of manufacture. Moreover, notwithstanding exercise of great care during manual cell handling, unacceptably high levels of cell breakage and reject cell/interconnector connections have been unavoidable.
There exists, therefore, a significant need for a practical automated machine for rapidly and safely placing interconnectors with precision onto individual solar cells and then for attaching the interconnectors to the solar cells. The present invention fulfills this need and provides further related advantages.